Thermostat



Oct. 9,- 1934. G. A. RoBERTsHAw THERMOSTAT 2 Sheets-Sheet l Filed April 2l, 1932 INVENTOR Oct. 9, 1934. i G A, RQBERTSHAW 1,976,517

THERMOSTAT Filed April 21, 1932 2 Sheets-Sheet 2 Patented Oct. 9, 1934 UNITED STATES THERMOSTAT George A. Robertslxaw, Montclair, N. J., assignor to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania y Application Api-11 21, 1932, semi No. 606,578

8 Claims.

'I'he present invention relates broadly to the art of temperature controlling devices, and more .particularly to thermostatic devices of the character adapted for example to domestic or 4industriai ovens and the uke, Whne it win hereinafter be referred to in connection with a domestic oven of the character found, for example, in a gas range, it will be understood that the utility of the invention is not thus limited, and the term 1 oven as herein utilized, unless specically limited, shall be construed as covering heating or temperature treating chambers broadly regardless of their particular construction, location or manner of operation.

In an effort to conserve space in ovens, at-

tempts have heretofore been made to mount the dial or other regulating `element directly on the door. Where such constructions have been proposed, in many cases the proper closing or easy opening of the door has not been possible without shock or damage to the thermostat. In order to overcome these disadvantages, it has also been proposed to locate thethermostatic control element entirely within the oven so as to be accessible only when the oven door is open.

The present invention relates generally to installations of the character referred to and has for one of its objects the provision of an improved thermostatic structure such that the difficulties and objections heretofore encountered are more or less completely obviated.

In the accompanying drawings, I have shown `for purposes of illustration only, certain preferred embodiments of the present invention, these drawings being largely diagrammatic.

In the drawings- Figure 1 is a front elevational view oi a domestic range constructed in accordance with the present invention;

Figure 2 is a detail sectional view through a portion of the range illustrating part of the temperature control mechanism;

Figure 3 is a horizontal sectional View showing the mechanism of Figures 1 and 2; and

Figure 4 is a detail sectional view, similar to Figure 2, illustrating a modied embodiment of the present invention.

In Figure 1 of the drawings, there is illustrated a domestic range 2 provided with the usual cooking top 3 and oven door 4. As is customary in the art, individual burner control handles 5 each adapted to controlthe i'low of gas from the manifold 6 to individual cooking burners (not shown) are provided. Communicating with the manifold is an oven burner pipe connection 7 adapted t0 be controlled by an oven valve 8, the construction being such that when the valve 8 is opened, gas may ilow into the connection 7. This connection communicates with the inlet of a tempera'ture responsive valve 9 fromthe outlet of 60 which extends a pipe 10 leading to an oven burner 1l, which may be of any .desired construction.

Located within the oven door 4, as shown more particularly in Figure 2, is a support 12 which carries a bi-metallic heat responsive strip 14 65 directly subjected to temperature conditions within the oven. This temperature responsive member has a pivotal mounting or fulcrum 15 at one end, and at its opposite end carries a valve 16. At its intermediate portion it is engaged by a screw 17 carried by a dial 18 projecting iorwardly through the door of the oven and carrying suitable graduations 19 adapted to be readv in conjunction with a pointer 20. 'Ihe action of the screw 17 is opposed by a spring 21, there- 75 by providing a structure such that as the pressure applied to the center of the member 14 is increased, there will be a tendency to bow the same as illustrated in Figure 2, while as the pressure is decreased, the member will tend to assume a straight position. The relationship of the bi-metallic parts of the member 14 is such that as the temperature to which the member" is subjected increases, the member will tend to bow as shown in Figure 2, and thus move the valve 16 away from its seat 22.

As will be clearly apparent from Figure 2 of the drawings, the seat 22 is carried bythe door of the oven, and on its side away from the valve 16 is adapted to engage a suitable washer 23 90 mounted in the end of a iitting 24 into which extends one end of a heat conduit 25. This heat conduit at its opposite end extends through a side wall 26 oi' the oven, as indicated for example in Figure 3, so as to discharge any uid medium conducted by it against a bulb 27, as indicated by the arrows 28. Thisfbulb, which may be of any conventional type, is adapted to contain an expansible iiuid the pressure of which may be communicated through a suitable connection 29 to the valve 9 in such manner that as the pressure of the fluid increases due to increased temperature conditions, the valve 9 will be closed to cut ofi the iiow of gas from the manifold 6 to the oven burner 11. 105

Having in mind the foregoing description, it. may be assumed that it is desired to maintain the oven at a temperature of approximately 550, substantially corresponding to the dial setting in Figure 2. The oven being cold, the valve 16 will 110 be in position on its seat 22, thus precluding the passage of any iluid from the oven chamber outwardly through the conduit 25.' The dial having been set, the oven valve 8 is opened to permit the flow of gas'from the manifold 6 into the burner 11, and the burner is lighted. After the burner has` been in operation for the required length of time to bring the oven to a temperature of 550, the bi-metallic member 14 will have been heated to such an extent that the valve 16 will have moved outwardly away from its seat 22 into the position illustrated in Figure 2. The heat pressure within the oven will cause a pressure flow of hot air outwardly from the oven Athrough the conduit 25 against the bulb 27, thereby heating this bulb and generating sufllcient pressure to close the valve 9.

This valve, being operated. by a vmotive fluid, is usually referred to as a motor operated valve or temperature responsive motor valve. The expansion of the fluid in the bulb 2'7 will close the valve 9, thus cutting off the further flow of gas from the manifold 6 to the oven burner. When the oven temperature drops below that corresponding to the dial setting, the valve 16 will again assume a position on its seat 22, thus preventing the flow of any heating medium through the conduit 25. l 'I'he bulb 27 will thus be permitted to dropr in temperature thereby decreasing the pressure of the motive fluid sufficiently to permit opening of the valve 9 and the resumption of gas flow to the burner 11. It will be understood that any desired type of pilot, not shown, may be provided for insuring the proper igniting of the gas and the desired operation of the parts.

In Figure 4, there is illustrated a slightly modifled embodiment of the invention wherein the conduit 30, corresponding to the conduit 25, is provided with a spring pressed collar 31 adapted to engage one side of the seat 32. This construction takes care of dimensional changes dueto different temperature conditions and always insures maintenance of a substantially tight seal between the conduit 30 and the seat 32.

In all cases the motor valve 9 will be of such construction that it will be open to permit the flow of gas to the burner at all temperatures below the minimum temperature at which the oven is ever to be operated. It may be assumed, for

example, that this 'temperature is equal to` approximately 250. yIn that case the motive fluid,

both as to kind and quantity, will be such that at any temperature below 250, the valve 9 `will be open. At any temperature above 250, the valve 9 will be closed. The bulb 27 will be so located that during. operation of the oven it will never be subjected to temperature conditions above 250 (in the example given) unless there is a ow through the conduit 25. Such a flow can only take place when the valve 16 is moved away from its seat, and this movement away from its seat does not occur until the desired temperature exists within the oven.

The present invention provides many installation and operating advantages. These advantages directly result from the use of twoithermostats, more or less remote one from the other and one carried directly by one wall of the oven or chamber, the temperature of which is to be controlled. Where this wall carrying such thermostat comprises a door, it will be apparent that the free opening and closing of the door is not impaired, the door yreadily moving away from the heat conduit when opened, and automatically assuming the desired relationship therewith when closed. In case the thermostat is carried by a. ilxed wall or closure, such a detachable connection is not required.

The bi-metallic or wall carried thermostat will operate within a narrow temperature range, the extent of which is determined by the construction thereof. A small opening movement of this wall carried thermostat immediately causes a suiilcient amount of heat, due to the pressure within the oven, to pass through the heat conduit and thus actuate the motor thermostat. Due to the high temperature conditions to which the motor thermostat may thus be subjected, it is possible to utilize a small and compact structure for this purpose, thereby materially conserving space and making it possible to utilize a simple and inexpensive structure. This is more especially true since this particular valve need only respond to one ypredetermined temperature condition, any temperatures in excess of that condition, within reason and such as would be encountered during normal use, not being harmful.

The bi-metallic valve is not subjected to the inaccuracies which Vresult -from the low bending strength o f bi-metallic strips in the case of strips which must move a considerable load. It has heretofore been necessary when utilizing bi-me- 'tallic control members, as distinguished from thermostats of the copper and carbon tube and rod type, for example, to provide extremely light springs. In such case, any increase for example in the gas press e, or variation in the friction of the parts, such s gland pins, has tended to cause a material temperature variation in the .operation of such structures, thereby preventing accurate temperature control. In the present structure the bi-metallic strip is subjected to practically no load, and may therefore be accurately constructed. The gas responsive valve 9, on the other hand, may be designed with springs of any desired' strength.

These advantages result from the division of the control between two temperature responsive devices wherein the bi-metallic temperature re- ,sponsive device constitutes a primary control which regulates the passage of a heating medium to the second device.

While I have herein illustrated and described certain preferred constructions useful in accordance with my invention. it will be understood that the constructon, arrangement andoperation of the parts may be widely varied without departing either from, the spirit of the invention or the scope of my broader claims.

I claim:

1. In a'heating system, an oven, a conduit extending from the interior of said oven outwardly through one wall thereof, a door abutting against one end of said conduit, a temperature responsive valve carried by said door for closing said conduit end, and a seco d temperature responsive valve operatively associated with the opposite end of said conduit.

2. In a stove having an oven the temperature 140 of which is to be controlled, a heat responsive combustible control valve, and a secondlheat responsive means subject to the temperature within said oven and controlling the delivery of an actuating medium to said first-mentioned valve.

3. In a stove having an oven the temperature of which is to be controlled, a. temperature responsive means responsive to temperature conditions within the oven, a temperature responsive valve for controlling the flow of a combustible for 150 heating said oven, and means controlled by said temperature responsive means for operating said valve.

4. In a stove having an oven the temperature o f which is to be controlled, a conduit for delivering a heating medium outwardly from said oven, a temperature responsive valve adjacent one end of said conduit for controlling the ow of a combustible for heating said oven, and a second temperature responsive means for controlling the ilow of a heating medium through said conduit.

5. In a stove having an oven the temperature of which is to be controlled, a primary heat responsive means, a secondary heat responsive means, and means for operating the secondary heat responsive means upon operation of the primary heat responsive means.

heat responsive means upon operation of the primary heat responsive means, said last-mentioned means including a conduit extending between said primary and secondary heat responsive means.

7. In a stove having an oven the temperature of which is to be controlled, a conduit within said oven and extending through one wall thereof, a heat responsive valve carried by said oven and controlling the ow of a heating medium through said conduit, and a combustible control valve responsive to the flow of a heating medium through said conduit.

8. In a stove having an oven the temprature of which is to be controlled, a conduit within said oven, a temperature responsive valve carried by said oven and adapted to open and close one end of said conduit, and a second heat responsive valve Ain operative relation to the opposite end of said conduit.

GEORGE A. ROBERTSHAW. 

